Governing valve for prime movers



p o. N. BRYANT GOVERNING VALVE FOR PRIME MOVERS Filed April 11, 1941 Flc1.

THRORT RRER RORT GREG REF! STRNDHRD DIFFUSER r wmR c I m N @m .h m 4a mmo mmluz mmmadm mutt L-IotIF .Exm mcwmm Sham Patented Sept. 29, 1942 asrarest FF! Q5.

GQVERNING VALVE FOR PRIME MOVERS Pennsylvania Appiication April 11,1941, Serial No. 388,021

Claims.

The invention relates to a governor valve for an elastic fluid or steamturbin and it has for an object to provide apparatus of this char cter:capable of covering a relatively wide of steam or elastic rluidpressures and which will .give substantially similar characteristicsthrougln out its entire stroke or lift.

For certain steam turbine applications, for example, an auxiliaryapplication such as for driving an auxiliary oil pump, the turbineshould be capable of covering a relatively wide range of steam orelastic fluid pressures. The steam pressure may vary from 100 to 1206pounds per square inch. The turbine nozzle area should be approximatelyinversely proportional to the steam pressure. It is desirable, for theseconditions, to provide a governor valve which will give substantiallysimilar characteristics throughout its entire stroke or lift.

The ordinary plug valve does not have a straight line relation betweenlift and steam now when the back pressure rises above to per cent of thesupply pressure. As may be seen from Patent No. 2,091,669, issued to thepresent applicant on August 31, 1937, and assigned to the WestinghouseElectric & Manufacturing Company, it i known that a difiuser valve doeshave a straight line relation between lift and steam flow even with backpressures as high as to Since it is good I per cent,of the supplypressure. practicewhere turbines are used to drive apparatus, such asauxiliary oil pumps, to provide excess nozzl area so that the turbinewill run satisfactorily even at reduced steam pressures, the backpressure will not ordinarily exceed 90 per cent of the supply pressure;however, a diffuser valve, such as disclosed in said patent, is notadapted to such extremes of steam flow and pressure, and, for thisreason, the diffuser becomes practically useless at small values ofsteam flow. What is required in a situation of this kind, and which itis the object of this invention to satisfy, is a valve having a diffuserexit area nearly in constant proportion to the valve annulus area and inwhich the annulus area is nearly proportional to the valve lift. It isalso desirable for 'the'lift to be relatively large in relation to theannulus area so as to facilitate control at small steam flows.

A further object of the invention is to provide a governor valve of thedifiuser type comprising a diffuser and valve members with such a rela-',tion of the difiuser passage and divergency of the valve member in thedirection of flow that a small change in ratio of exit area to annulusarea occurs over the whole range of lift of the Valve member.

A further object of the invention is to provide, in connection with agovernor valve comprising diiiuser and valve members, the diffusermember having a diiiuser passage including an upper part which isconvexly curved in the direction of flow to provide convergent, throatand divergent portions and a lower conical divergent part into which thecurved divergent portion merges, the valve member being conicallydivergent in the direction of flow and cooperating with thconvexly-curved divergent portion of the difiuser passage to define anannulus area and with the conically divergent portion of such passage todefine an exit area, such relation of diffuser passage and valve membersurfaces that a small change in ratio of exit area to annulus areaoccurs over the entire range of lift of the valve member.

These and other objects are effected by the invention as will beapparent from the following description and claims, taken in connectionwith the accompanying drawing forming a part of this application, inwhich:

Fig. l is a diagrammatic view showing a steam turbine having theimproved governor valve applied thereto;

Fig. 2 is a sectional View showing the preferred form of governor valve;

Fig. 3 is a view similar to Fig. 2 but showing a modified form of thegovernor valve; and,

Fig. 4 is a graph showing operating characteristics of the valve.

Referring now to the drawing more in detail, in Fig. 1, there is shown asteam turbine, at it, having nozzles H for supplying steam at highvelocity to suitable blading (not shown). Motive steam is supplied to thturbine by means of the conduit or passage [2 provided with the governorvalve, at 14.

The governor valve includes diffuser and valve members I5 and IS, thevalve member being joined to a stem ll operatively connected to suitableservo-motor apparatus, at It. Suitable servo-motor apparatu forcontrolling the movable valve member is more particularly described inthe application of A. F. Schwendner et 211., Serial No. 381,804, filedMarch 5, 1941.

The difiuser member It has a diffuser passage 26 comprising a first part2!. and a second part 22. The first, Or upper, part includes convergent,throat and divergent portions 23, 24, and 25, respectively, and at leastthe convergent and divergent portions are convexly curved in thedirection of flow. The second, or lower, part 22 is conically divergentand the divergent portion 25 of the first part merges thereinto.

The valve member 16 has a conical surface 26 which diverges in thedirection of fiow. The upper or apical end of the valve member isrounded or faired, as shown at 21. The lower or basal end of the valvemember is joined to the valve stem ll, the latter being operativelyconnected to the servo-motor apparatus, at 18.

The conical surface 26 of the valve member has a small angle ofdivergence in relation to the conical surface of the second part 22 ofthe diffuser passage so that there occurs, over the whole range of liftor stroke of the valve member IS a small change in ratio of exit area,defined between the conical surface 26 of the valve member at the loweror basal end of the latter and the conical surface 22, and the annulusarea, defined between the conical surface 26 and the curved divergentportion 25 of the diffuser passage. As shown in Fig. 2, the angle ofdivergence B of the lower conical part 22 of the diffuser passage is 60and the angle of divergence A of the valve member surface 26 is 45,thereby providing an angle of divergence of 15 between the surfaces 26and 22. Fig. 3 is similar to Fig. 2 except that the angles B and A arelarger, B being 75 and A, 60".

The radius of curvature C of the convexlycurved upper part of thdiffuser passage is preferably one-third of the diameter of the throatportion 24, the diameter being indicated at D.

The diameter F of the stem I1 is preferably made equal to the throatdiameter D so that a practically constant steam unbalance may be imposedon the valve member for the entire range of travel of the latter.

A valve, such as described, is advantageous in that a high, uniformdiffuser area ratio occurs over the entire range and this makes possiblea substantially constant relation as between lift and steam flowregardless of back pressure. Furthermore, the improved valve providesfor relatively greater lift, for a given steam flow and for a very highflow coefficient at all lifts. These advantageous relations will beapparent from a consideration of Fig. 4. In Fig. i, the curve d showsthat the diffuser area ratio, that is, the ratio of exit area to annulusarea for Fig. 2

changes through the small amount of from 2.75

to 3.25 over the whole range of lift. Similarly, the curve e of Fig. 4shows that this ratio changes through the small amount of 2.2 to 2.6over the whole valve lift range of the valve of Fig. 3.

While the invention has been shown in several forms, it will be obviousto those skilled in the art that it is not so limited, but issusceptible of various other changes and modifications without departingfrom the spirit thereof, and it is desired, therefore, that only suchlimitations shall be placed thereupon as are specifically set forth inthe appended claims.

What is claimed is:

1. In a governor valve for an elastic fluid turbine, means providing anelastic fluid chamber: means for conducting elastic fluid from thechamber to the turbine and including a diffuser member: said diffusermember having a diffuser passage comprising first and second parts andthe first part converging in the direction of flow to a throat and thendiverging: said convergent and divergent portions of the first part ofthe diffuser passage being convexly curved in the direction of flow:said second part of the diffuser passage being conically divergent andmerging into said curved divergent portion of the first part: and avalve member including a conical head and a stem joined to the basal endof the latter: said head diverging in the direction of flow, defining,with said second part of the diffuser passage an exit area, anddefining, with said curved divergent portion an annulus area; and theangle of divergence of the head being sufficiently less than the angleof divergence of said second part of the diffuser passage to provide fora substantially constant ratio of exit area to annulus area over thewhole range of lift of the valve member in order that the relationbetween fiow and lift may remain substantially uniform.

2. In a governor valve for an elastic fiuid turbine, means providing anelastic fluid chamber: means providing a passage for conducting elasticfluid from the chamber to the turbine and including a diffuser member:said diffuser member having a diffuser passage comprising first andsecond parts and the first part converging in the direction of fiow to athroat and then diverging: said convergent and divergent portions of thefirst part of the diffuser passage being convexly curved in thedirection of flow: said second part of the diffuser passage beingconically divergent and merging into said curved divergent portion ofthe first part: and a valve member including a conical head and a stemjoined to the basal end of the latter: said head diverging in thedirection of flow, defining, with said second part of the diffuserpassage, an exit area, and defining, with said curved divergent portionof the first part of the diffuser passage, an annulus areagsaid stemhaving a diameter equal to the throat diameter of the diffuser passage;and the angle of divergence of the head being sufficiently smaller thanthe angle of divergence of said second part of the diffuser passage toprovide for a substantially constant ratio of exit area to annulus areaover the whole range of lift of the valve member in order that therelation between fiow and lift may remain substantially uniform.

3. In a governor valve for an elastic fluid turbine, means providing anelastic fluid chamber: :rneans providing a passage for conductingelastic fluid from th chamber to the turbine and including a diffusermember: said diffuser member having a diffuser passage comprising firstand second parts and the first part converging in the direction of flowto a throat and then diverging: said convergent and divergent portionsof the diffuser passage being convexly curved in the direction of flowabout a radius of curvature of the order of one-third of the throatdiameter: said second part of the diffuser passage being conicallydivergent and merging into the curved divergent portion of the firstpart: and a valve member including a conical head and a stem joined tothe basal end of the latter; said head diverging in the direction offlow, defining, with said second part of the diffuser passage, an exitarea, and definining, with said curved divergent portion of the firstpart of the diffuser passage, an annulus area; said stem having adiameter equal to the throat diameter of the diffuser passage; and theconical divergent surface of the valve member and the conical divergentsurface of the second part of the diffuser passage having an angle ofdivergence in the direction of flow of the order of 15 to provide for asubstantially constant ratio of exit area to annulus area over the wholerange of lift of the valve member in order that the relation betweenflow and lift may remain substantially uniform.

4. The combination as claimed in claim 3 wherein the angle of divergenceof the divergent conical surface of the second part difiuser passage is75 and the angle of divergence of the valve member conical surface is60".

5. In a diffuser valve for an elastic-fluid turbine, a diffuser having apassage including a first part followed in the direction of fluid flowby a second part: said first part including convergent, throat anddivergent portions and the convergent and divergent portions beingcurved convexly in the direction of flow about a radius equalapproximately to of the throat diameter: said second part beingconically divergent and the convexly-curved divergent portion of thefirst part merging into the latter: and a valve including a conical headand a stem joined to the basal end of the latter: said head diverging inthe direction of flow at an angle sufficiently less than the angle ofdivergence of said conically divergent second part of the diffuserpassage to provide a small change in ratio of exit area, defined betweenthe basal end of the conical head and the diffuser passage conicalsurface, to annulus area, defined between the convexly-curved divergentportion of the first part of the diffuser passage and the conical head,over the whole range of valve lift in order that the relation betweenflow and lift may remain substantially uniform; and said conical headand the stem having a diameter approximately equal to that of saidthroat.

OZRO N. BRYANT.

